/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package axil.stdlib.collection.function;

import axil.api.AxilObject;
import axil.api.extend.Environment;
import axil.api.extend.Function;
import axil.api.extend.Parameters;
import axil.api.extend.Source;
import axil.engine.function.Functor;
import axil.stdlib.collection.type.Dict;
import axil.stdlib.core.type.Nil;
import axil.vm.stack.StackFrame;

import static axil.framework.Functions.callable;
import static axil.framework.Functions.iter;


/**
 * Given a collection and a function, evaluate each object in the collection
 * through the function, returning a key. A dictionary results from the mappings.
 * For example:
 *
 * 		map(list(5, 6, 7), func(o, o * 2))
 *
 * Yields this dictionary:
 *
 * 		10 -> 5, 12 -> 6, 14 -> 7
 *
 * If the collection given is empty, then an empty dictionary is returned. If
 * the collection given is nil, then nil is returned.
 */
public class MapF implements Function {

	/**
	 * Execute this function with the given arguments. The Axil compiler will
	 * ensure that the number of arguments passed to the function are valid.
	 * If this function fails during execution for any reason, then an exception
	 * is thrown.
	 */
	public AxilObject eval(Environment env, Parameters params, Source source) {
		AxilObject a = params.a();
		if (a == Nil.object) {
			return a;
		}
		Functor func = callable(params.b());
		StackFrame sf = StackFrame.create(params, source, func.ids());
		Dict dict = new Dict();
		for (AxilObject v : iter(a)) {
			sf.a(v);
			AxilObject k = func.call(env, sf);
			dict.at(k, v);
		}
		return dict.immute();
	}
}
